In much of the developed world, air-conditioning has become a near necessity. In the U.S., most newly constructed housing units are centrally air-conditioned. Many dwelling units in the U.S. have central air-conditioning and/or one or more room air-conditioners. Virtually all-commercial building space in the U.S. is air-conditioned.
As a result of air-conditioning's widespread use, electrical energy consumed by air-conditioning amounts to at least 50% of total annual residential use. The contribution of residential air-conditioning to the peak power consumption is even more significant, approaching 80% of residential peak power demand and 60% in the commercial sector. Refrigeration for commercial and residential use is the second major source of electricity consumption.
In cold climates, the energy consumed for space-heating and hot water supply represents a high percentage of the total energy consumption in service sector buildings, and an even higher percentage in the residential buildings.